P53-Mediated G1/M Checkpoint Controls Altered by PPM1D

描述（由申请人提供）：p53介导的G1/M检查点控制被PPM1D改变p53肿瘤抑制蛋白是一种序列特异性转录因子，可调节细胞对基因毒性应激和其他形式的细胞应激的反应。PPM1D（正式称为Wip1）在基因毒性应激反应中以p53依赖的方式被转录激活。它编码一种蛋白磷酸酶，靶向应激诱导的激酶p38MAPK，破坏p38MAPK-p53信号通路。这与p53蛋白n端磷酸化模式的改变有关。n端磷酸化是p53蛋白发挥转录因子功能的重要条件。我们和其他人已经证明，强迫外源表达PPM1D会减弱细胞对dna损伤剂的凋亡反应。由于基因扩增，PPM1D在人类肿瘤细胞中组成性过表达，从而降低PPM1D，增强了对化疗药物的凋亡反应。这与促凋亡Bax基因表达水平的变化有关。该项目的目标是阐明PPM1D在调节p53转录活性中的机制基础和作用。待验证的假设是PPM1D对p38MAPK-p53信号通路的破坏会影响p53介导的参与细胞周期检查点控制和/或凋亡的应答基因的转录。具体目的如下：1)确定ppm1d介导的p38MAPK-p53信号的破坏是否会改变p53蛋白与下游靶基因p53应答元件之间的相互作用。2)确定ppm1d介导的p38MAPK-p53信号的破坏是否会改变p53蛋白与转录辅激活因子的相互作用。3)鉴定和表征因ppm1d介导的p38MAPK-p53信号通路中断而改变表达的基因。摘要：PPM1D是p53网络中的一个新成员，目前我们对其知之甚少。PPM1D基因通常在人类乳腺、卵巢和神经母细胞瘤肿瘤中扩增，这些肿瘤含有野生型p53基因。本项目将为PPM1D在参与细胞周期调控和凋亡的p53网络中所起的作用提供新的信息，并阐明其作用的机制基础。

DESCRIPTION (provided by applicant): P53-Mediated G1/M Checkpoint Controls Altered by PPM1D The p53 tumor suppressor protein is a sequence-specific transcription factor that modulates the response of cells to genotoxic stress and other forms of cellular stress. PPM1D (formally called Wip1) is transcriptionally-activated in response to genotoxic stress in a p53-dependent manner. It encodes a protein phosphatase that targets the stress induced kinase p38MAPK which disrupts the p38MAPK-p53 signaling pathway. This is correlated with alterations in the pattern of N-terminal phosphorylation on p53 protein. N-terminal phosphorylation is important for p53 protein to function as a transcriptional factor. We and others have shown that forced exogenous expression of PPM1D attenuates the apoptotic response to DNA-damaging agents. Decreasing PPM1D in human tumor cells that constitutively over express it due to gene amplification enhances the apoptotic response to chemotherapeutic agents. This is correlated with changes, in the level of expression of the pro-apoptotic Bax gene.The goal of this project is to elucidate the mechanistic basis and the role that PPM1D plays in modulating the transcriptional activity of p53.The hypothesis to be tested is that disruption of the p38MAPK-p53 signaling pathway by PPM1D affects p53-mediated transcription of responsive genes involved in cell cycle checkpoint control and/or apoptosis. The Specific Aims are the following: 1) To determine if PPM1D-mediated disruption of p38MAPK-p53 signaling alters the interaction between p53 protein and p53-responsive elements of downstream target genes. 2) To determine if PPM1D-mediated disruption of p38MAPK-p53 signaling alters the interaction of p53 protein with transcriptional coactivators. 3) To identify and characterize genes whose expression is altered by PPM1D-mediated disruption of the p38MAPK-p53 signaling pathway. Lay Abstract: PPM1D is a new player in the p53 network about which we know very little at present. The PPM1D gene is often amplified in human breast, ovarian and neuroblastoma tumors that harbor a wild type p53 gene. This project will provide new information regarding the role that PPM1D plays in the p53 network involved in cell cycle control and apoptosis and elucidate the mechanistic basis for this action.